1. Field of the Invention
This invention relates to an imaging apparatus wherein the observing wavelength range can be selected in response to an observed object and an endoscope apparatus using the same.
2. Related Art Statement
Recently, there are suggested various electronic endoscopes wherein a solid state imaging device such as a charge coupled device (CCD) is used for an imaging means.
The electronic endoscope has advantages because the resolution is higher than in a fiberscope, it is easy to record and reproduce picture images and treatment of picture images such as enlargement and the comparison of two picture images are easy.
When observing an object by using an imaging device as of the above mentioned electronic endoscope and particularly when distinguishing an affected part and normal part from each other within a living body, it is necessary to sense (recognize) a delicate color tone difference. However, in case the difference of the color tone in the observed position is delicate, a high degree of knowledge and experience will be required to sense this delicate difference, a long time will be required until it is detected and it has been difficult to always properly judge the difference even if cautious forces are concentrated while sensing.
In order to cope with this situation, for example, in the gazette of Japanese Patent Laid Open No. 3033/1981, there is disclosed a technique wherein, by noting that the difference of the color tone may be large in a range other than the visible range as, for example, an infrared wavelength range, a spectral light having at least one infrared wavelength range is led in time series to illuminate an object to be observed. The reflected light from the object is imaged in a solid state imaging device and is converted to an electric signal. The electric signal is processed in response to the wavelength range and a picture image of the wavelength range is displayed by a specific color signal. According to this related art example, the invisible information obtained in the infrared wavelength range can be converted to visible information and, for example, the affected part and normal part can be quickly and easily discriminated from each other.
However, in the above mentioned related art example, since the observing wavelength range is fixed, for example, there are disadvantages that, when infrared light is utilized, no picture image of a general visible range will be obtained, it will be difficult to compare both picture images and there will be no effect on an observed object characteristic in another wavelength range.
Also, for example, in the gazette of Japanese Patent Laid Open No. 139237/1984, there is disclosed a technique that a plurality of picture images are taken by passing a fluorescence generated from a living body in response to an excited light radiation through a plurality of types of band pass filters and respectively different color tones are alloted to the density grade differences of the respective picture images to form respective quasi color picture images.
However, in this related art example, the density difference can be discriminated but the color tone difference can not be discriminated.